September 29, 2011: Physical Processes and Evolutionary Consequences

Three vignettes of different scales of flow and landscape influence on biotic process will be presented. 1) The Late Precambrian Rangeomorph fauna of Mistaken Point Newfoundland constitute the earliest community of large multicellular organisms. Through flow modeling we demonstrate that these organisms evolved large size to access higher velocities in a low flow environment. Access to velocity overcomes diffusional limits to resource acquisition in a community dependant on dissolved resources, providing the impetus to the evolution of large multicellular form. 2) Rapid landscape evolution of the Society Islands resulted from recent sea-level fall from a mid-Holocene maximum. This fall first generated a plethora of reef-top atolls in Polynesia. In the last two millennia such islands have been eliminated preferentially from the south-sides of the Society Islands as a consequence of wave energy from the Southern Ocean, yielding dramatic change of reef and lagoon environments with attendant consequences for marine life and the human population. 3) Coastal estuaries of California have undergone a maturation process during the Holocene converting many estuaries from bays to lagoonal systems dominated by the episodic/seasonal stream flow of our Mediterranean climate. The impacts of the inter-annual details of stream flow on dispersal of a seasonal-lagoon specialist fish, the tidewater goby, are examined using high-resolution genotyping. Conservation genetic and estuarine restoration issues are touched upon.

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